Originally Posted by FlaD90
I can't see to find a local source for Mordent T-Wash solution, anyone have a source to point out?
POR15 has a product called Metal-Ready which can be used to etch & clean galvanized metal, this is available at my local paint shop.,..but just trying to find another product.
From Acron's site: http://www.acronpaints.co.uk/cgi-bin...s/mordanttwash
As I understand it, mordant solutions are conversion coatings to zinc phosphate. This theoretically prevents surface adhesion problems that paint has to zinc oxide films. Simple etching of the surface does not appreciably improve adhesion performance.
Depending on the concentration of phosphoric acid, the reaction can be quite vigorous. Someone else probably knows how long you should leave a part in the bath. At 37% dilution, I have read one half hour maximum, but that is from Ospho. The surface should be darker in appearance after proper application of the zinc phosphate film. You may end up with some parts that have a white surface film of some form of iron phosphate (maybe II or III), which should be scrubbed away. I believe this is due to the presence of free iron in the surface of the material (but I could be wrong about that...)
Generally speaking Iron or Ferrous Phosphates have poor surface adhesion to galvanized surfaces and should be removed.
Similar problems happen with aluminum paint jobs where the paint shop fails to utilize chromate conversion on the panels, leading to poor adhesion on the thin and brittle aluminum surface oxides.